Women begin using cocaine, enter treatment at earlier ages than men, and have more severe cocaine use at intake than men. Thus, women progress from initial use to dependence faster than men do. This telescoping effect reflects a briefer time course for the development of medical consequences and behavioral/psychological factors characteristic of a dependence disorder. The studies proposed are a fundamentally important first step towards understanding structure-function relations in the induction and expression of drug-taking behavior and the long-term consequences of this behavior in both males and females. In this proposal we seek to identify the hormonal and developmental events that produce a sexually dimorphic ascending dopamine system that results in sex differences in drug abuse liability, and to identify some of the associated neural processes that mediate these sex differences. There are two times during development of the brain when hormones can influence its organization. In the rat these occur during the peri-natal period and again during the peri-pubertal period. Experiments are proposed to test the hypothesis that the enhanced vulnerability of females for cocaine abuse is dependent on the lack of exposure to gonadal hormones during the critical perinatal period, as well as subsequent exposure to ovarian hormones during the peripubertal period. Self-administration of cocaine will be used as the primary outcome measure. Acquisition of drug taking behavior during adolescence in humans is a strong predictor of drug abuse problems as an adult. We hypothesize that onset of hormone exposure during the peri-pubertal period contributes to increased vulnerability for the reinforcing and/or long-term consequences of cocaine treatment in both males and females. We will determine whether adolescence is a period of enhanced vulnerability for female vs. male rats to self-administer cocaine. Alternatively, it is possible that adolescents aren't more vulnerable to the addictive properties of the psychomotor stimulants, but that the long-term consequences of exposure to these drugs during adolescence result in increased susceptibility as an adult, this possibility will be examined as well. Finally, the neural basis of the organizational and developmental influences on sex differences in the response to cocaine will be examined by looking at dopamine in dialysate from striatum and nucleus accumbens. These experiments are a first step towards exploring the extent that sex differences in vulnerability for cocaine abuse impacts the striatum and nucleus accumbens.